JPS6249573B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a graphite tube device used in flameless atomic absorption spectrometry, and more particularly to a graphite tube device suitable for accommodating a sample holder in a predetermined orientation.

During a conventional atomic absorption spectroscopy measurement, a graphite tube is placed in the optical path and the sample to be measured is placed on a sample holder outside the optical path within the tube. The sample is then atomized in a known manner and its measurement performed. The test sample is typically placed into a sample holder through an inlet hole in the graphite tube wall.

In particular when testing liquid samples, it has been found to be highly advantageous to position the sample holder at a preselected angle from the center line of the inlet hole. Furthermore, in order to always obtain reliable results, it has proven to be of great advantage if the sample holder can be replaced while maintaining the same orientation relative to the inlet hole, or if the same holder can be removed and reinserted. That is, the preselected orientation must be the same for each holder inserted into the tube.

It is known from US Pat. No. 4,111,563 that the sample holder can be an integral part of the graphite tube structure. Although this is advantageous in maintaining a predetermined angle between the holder and the graphite tube inlet hole, it has the disadvantage that the holder cannot be replaced or removed without destroying the graphite tube. Therefore, if the sample holder must be replaced for some reason, the apparatus of the above-mentioned US patent requires replacement of the entire graphite tube.

In view of the above-mentioned prior art, it is an object of the present invention to make it possible to precisely position such a holder with respect to the inlet hole of a graphite tube, while at the same time making the sample holder replaceable.

Another object of the invention is to provide a graphite tube device in which the inserted sample holder can withstand external mechanical shocks such as those occurring during sample injection.

This purpose uses according to the invention a shaped sample holder with a sample receiving recess, which holder has a support surface in the graphite tube and the holder can be removed and repositioned or replaced in the same orientation in the graphite tube. The problem is solved by fitting the problem in a certain way.

Next, the present invention will be explained with reference to the drawings.

According to an advantageous embodiment of the invention shown in FIG. 1, a graphite tube arrangement, generally designated 10, includes a graphite tube 12 having an outer cylindrical surface 14 and an inner cylindrical surface 16 concentric therewith.
Consisting of The outer surface 14 and the inner surface 16 have inlet holes 20
A wall 18 having a partition wall 18 is partitioned. Graphite tube 1 with inlet hole 20
The special position with respect to the periphery of 2 will be described later. As is known in the art, the tube 12 is placed or aligned in the optical path through which the light beam through which the atomic absorption properties of the sample are to be determined is measured.
Graphite tube 12 also includes means for positioning sample holder 22 in a selected orientation relative to inlet aperture 20. In this embodiment, the orientation means are a set of generally parallel grooves 24 formed in the inner surface 16 of the graphite tube 12. Details of the groove 24 will be described later.

In addition to the graphite tube 12, the apparatus 10 has a sample holder 22, which in this embodiment has a substantially trapezoidal cross section. As shown, the hoop of the trapezoidal support is formed such that a relatively wide surface 26 which, together with side surfaces 30, defines an acute angle 28 is slidably engaged with a groove 24 formed in the inner surface 16 of the graphite tube 12. The platform 22 can therefore be inserted into the tube 12, removed, reinserted, or replaced with another platform having the same cross-sectional shape without changing its orientation within the tube 12. As shown in FIG. 2, sample holder 22 has a recess 32 in its relatively narrow surface. Recess 32 is configured to hold the amount of test sample necessary to perform flameless atomic absorption spectroscopy. For known reasons, sample holder 22 is formed from a non-porous material. It has been determined that the platform 22 must be oriented such that the offset angle 36, defined as the acute angle between the normal 38 to the relatively narrow surface and the axis 38 of the inlet hole 20, is on the order of about 27°. . It has been found that an offset angle 36 of 27° is advantageous for inserting a liquid sample from the inlet hole 20 into the graphite tube 12. In fact, this angle is advantageous when a pipette, not shown, is inserted through the inlet hole 20 to dispense a liquid sample into the recess 32. Another advantage besides the reproducibility of the orientation of the platform 22 is that the mating surface holds the platform firmly in a fixed position. In this way, the device 10 can withstand external physical shocks impinging on the graphite tube 12 without a change in the orientation of the platform.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the graphite tube device, and FIG. 2 is a plan view of the sample holder. 10...graphite tube device, 12...hollow graphite tube, 1
8...wall, 20...inlet hole, 22...sample holding stand, 32...recess.

Claims (1)

[Claims] 1. A graphite tube suitable for the passage of a light beam, having an inlet hole passing through the tube wall, and a sample holder with a recess on one side for holding the sample to be tested, which A sample holder is disposed outside the optical path within the graphite tube, the sample holder and the graphite tube having mating surfaces for positioning the pedestal in a predetermined orientation within the graphite tube, whereby the sample holder Graphite tube device for use in flameless atomic absorption spectroscopy, characterized in that the pedestal can be removed and reinserted or replaced with another similarly shaped pedestal in said predetermined orientation. 2. The sample holder has a trapezoidal cross-section with a relatively narrow side and a relatively wide side, the relatively wide side being separated from the relatively narrow side by a pair of side faces forming an acute angle with the relatively wide side. Claim No. 1
Apparatus described in section. 3. Claim 2, wherein the graphite tube is provided with a set of grooves suitable for accommodating a sample holder, into which the acute angle portion formed by the side surface and the relatively wide surface fits. Apparatus described in section. 4. The apparatus of claim 2, wherein the sample holder is oriented such that the normal to the relatively narrow surface forms an acute angle with the axis of the inlet hole. 5. Claim 4, wherein the acute angle is approximately 27°.
Apparatus described in section. 6. The device according to claim 2, wherein the relatively narrow surface of the sample holder is provided with a recess.